The present invention relates to an information delivery system for delivering multimedia information through the use of the radio technology.
The IS-95 radio system that is currently used in Japan and the IMT-2000 that will be used in near future employ the CDMA technology, in which one mobile station enables to receive two or more traffic channels on the same frequency band at a time. For example, the IS-95 radio system makes it possible to simultaneously receive five traffic channels each having a transmission speed of 14.4 Kb/s, thereby leading to the communication at a transmission speed of 72 Kb/s.
The reception of plural traffic channels on one mobile station at a time is made possible in the case that the mobile station is located in the so-called excellent wave circumstances, that is, the wave circumstances that the signal power is high but the noise power is low. That is, in this type of radio communication system, one mobile station has so fast a transmission speed that it may receive plural radio channels, while another mobile station has so slow a transmission speed that it may receive only one radio channel. Hence, in such a radio communication system that the transmission speed of the wireless interval may be changed according to the wave circumstances such as the signal power and the noise power, in a case that the same information is multicast or broadcast to a plurality of mobile stations and the base station cannot control the transmission power for each mobile station, it is necessary to suit the information delivery to the mobile station having the slowest transmission speed of the associated mobile stations. For this purpose, the base station apparatus has to maximize the transmission power so that the information may be positively delivered to all the mobile stations. However, the maximization of the transmission power of the mobile station apparatus brings about any interference to be given to another radio channel within the same frequency band, which radio channel may be often used for speech or another information delivery.
It is an object of the present invention to provide an information delivery system which may vary an information amount and the quality of service received by the use according to the radio circumstances of the mobile station as considering any interference to be given to another communication in the multicast or broadcast information delivery in which the same information is delivered to all users. That is, the information delivery system may be designed so that the mobile station under the bad wave circumstances enables to deliver the information with the highest priority to be inevitably delivered, while the mobile station under the good wave circumstances enables to receive the information with the higher priority and the additional information.